Hi list,
I am trying to work out why I would want to use pgr_alphaShape and
Pgr_pointsAsPolygon with the results of a pgr_dirvingDistance.
All 3 functions are enabled when 'Driving Distance' is enabled so logical
I assume that they are deisgned to be used together.
I can take the results of a driving distance, which gives me a list of
points, look up this list in by node table, which gives me a list of x/y
values, I can then create a polygon from this list which will give me what
I am after
What will pgr_pointsAsPolygon/pgr_alphashape enabled me to do in this
context?
dave
On 11/11/2014 3:30 AM, dave.potts@pinan.co.uk wrote:
Hi list,
I am trying to work out why I would want to use pgr_alphaShape and
Pgr_pointsAsPolygon with the results of a pgr_dirvingDistance.
All 3 functions are enabled when 'Driving Distance' is enabled so logical
I assume that they are deisgned to be used together.
I can take the results of a driving distance, which gives me a list of
points, look up this list in by node table, which gives me a list of x/y
values, I can then create a polygon from this list which will give me what
I am after
What will pgr_pointsAsPolygon/pgr_alphashape enabled me to do in this
context?
Dave,
These features were not available in postgis in earlier version. Basically they were used to create concave polygons that represent the isochrones for the driving distance.
The code will get reviewed at the next major release and if it is obsoleted by the postgis code then we might consider removing them and just creating a wrapper that simplifies/automates creating the isochrones.
-Steve
On 11/11/14 18:00, Stephen Woodbridge wrote:
On 11/11/2014 3:30 AM, dave.potts@pinan.co.uk wrote:
Hi list,
I am trying to work out why I would want to use pgr_alphaShape and
Pgr_pointsAsPolygon with the results of a pgr_dirvingDistance.
All 3 functions are enabled when 'Driving Distance' is enabled so logical
I assume that they are deisgned to be used together.
I can take the results of a driving distance, which gives me a list of
points, look up this list in by node table, which gives me a list of x/y
values, I can then create a polygon from this list which will give me what
I am after
What will pgr_pointsAsPolygon/pgr_alphashape enabled me to do in this
context?
Dave,
These features were not available in postgis in earlier version. Basically they were used to create concave polygons that represent the isochrones for the driving distance.
The code will get reviewed at the next major release and if it is obsoleted by the postgis code then we might consider removing them and just creating a wrapper that simplifies/automates creating the isochrones.
Thank you Steve, for clearing up that point.
Dave.
-Steve
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